A letter series is given below in which some letters are missing. Select the option that gives the letters that can fill these blanks in that order.

s_ss_as sa_cb_s sas_ba_

 absass

After dividing the series in 3 parts of 7 letter each we get s_ss_as / sa_sb_s / sas_ba_.

On comparing different positions we get sassbas as a repetitive term.

sassbas / sassbas / sassbas

So the code required for the series is absass